A LINEAR SOLUTION TO THE KINEMATIC PARAMETER-IDENTIFICATION OF ROBOT MANIPULATORS

An important step in a model-based robot calibration process is the id entification of the manipulator's unknown kinematic model parameters f rom end-effector pose measurements and robot joint position readings a t known measurement configurations. A linear solution method for the u nknown kinematic parameters directly from the forward kinematic model is presented. The proposed method requires the use of neither a normal model nor a linearized error model of the robot. Such a solution is p ossible for two reasons: 1) the use of a special robot kinematic model ing convention known as the CPC model, in which the independent CPC li nk parameters appear linearly in the system of equations to be solved; and 2) the use of a particular sequence of robot pose measurements. T he CPC orientation parameters of the revolute joints are first determi ned recursively under the condition that the pose measurements of the robot are taken while releasing each revolute joint one at a time and successively. The remaining CPC parameters are then computed in terms of the orientation parameters obtained earlier. For explicit solution formulas of an n degree-of-freedom manipulator, end-effector pose meas urements from n + 1 configurations need to be acquired. Additional pos e measurements can be handled by least squares techniques. Some practi cal issues related to kinematic parameter identification with the prop osed approach are addressed through simulation studies.